DESCRIPTION: The investigator proposes experiments which will identify the specific phosphodiesterase forms present in mouse skeletal muscle. Alterations in cAMP activity are associated with Duchenne Muscular Dystrophy and previous studies have suggested that altered levels of PDE are responsible for diminishing cAMP levels. The investigator will determine which of the seven isoforms are present in muscle using HPLC and RT-PCR measurements of protein and RNA respectively. The investigator will then determine whether the disease leads to global affects on PDE or whether specific isoforms are altered in the pathophysiological state by comparing control and mdx mice. For this purpose RNA levels will be quantitatively compared by RPA measurement and protein levels will be compared by measuring enzymatic activity in HPLC fractions and by Western Blot analyses.